1. Field of the Invention
The present invention relates to an image forming apparatus and a light emitter substrate.
2. Description of the Related Art
Conventionally, an image forming apparatus which acts as an electron-emitting apparatus using an electron-emitting device has been known. More specifically, as the image forming apparatus like this, for example, a flat type electron displaying panel in which an electron source substrate on which a number of cold cathode electron-emitting devices are formed and an anode substrate which is equipped with a metal back for accelerating the electrons emitted by the electron-emitting devices and or a transparent electrode and a fluorescent body are parallelly opposed to each other has been known. Here, the space between the electron source substrate and the anode substrate has been exhausted and vacuumized. Such an image forming apparatus using a field-emission electron-emitting device {or an FEA (Field Emitter Array) device} is well known.
FIG. 16 is a diagram schematically illustrating the constitution of an electron beam displaying panel as an example of the image forming apparatus using the electron-emitting device. More specifically, in FIG. 16, the electron beam displaying panel includes an electron source substrate 109, a face plate 102 being an anode substrate, a side wall 104, a rear plate 101, and a spacer 103 for defining an interval between the rear plate 101 and the face plate 102, thereby constituting a vacuum envelope. Further, the electron beam displaying panel includes electron-emitting devices 108, row-direction wirings 105 and column-direction wirings 106. The row-direction wirings 105 and the column-direction wirings 106 are respectively connected to device electrodes. Furthermore, the electron beam displaying panel includes a transparent electrode (anode) 116 and a fluorescent body (fluorescent film) 110.
To produce an image in the electron beam displaying panel, a predetermined voltage is first applied sequentially to the row-direction wirings 105 and the column-direction wirings 106 which are arranged like a matrix, thereby selectively driving the predetermined electron-emitting device 108 positioned at the cross point of the matrix. Then, electrons thus emitted are irradiated to the fluorescent body 110, thereby obtaining a light spot. Incidentally, in order to obtain the high-luminance light spot by accelerating the emitted electrons, a high voltage is applied to the transparent electrode 116 through a high voltage terminal Hv to have a high voltage as compared with the electron-emitting device 108. Here, although according to the performance of the fluorescent body, the voltage to be applied is set to several hundreds volt (V) to several tens kilovolt (kV). Accordingly, a distance d between the rear plate 101 and the face plate 102 is generally set to several hundreds micrometer (μm) to several millimeter (mm) so that vacuum dielectric breakdown (that is, electric discharge) due to the applied voltage does not occur.
In the image forming apparatus like this, as illustrated in FIG. 2, the electron beams irradiated to the face plate are back-scattered, and the scattered beams re-enter the face plate due to an electric field. If the back-scattered electrons re-enter the fluorescent body, unnecessary portions of the fluorescent body emit light, thereby occurring a phenomenon called halation. The halation prevents a flat panel image forming apparatus from achieving high contrast and high color purity.
To solve such a conventional problem as described above, each of Japanese Patent Application Laid-Open Nos. H06-338273 and 2002-033058 discloses a proper method. In the relevant method, for example, as illustrated in FIG. 3, a rib (barrier) 14 which is set to have a predetermined height is arranged on a black member 12 on the side of the surface of a face plate 2 opposite to a rear plate. The rib 14 functions to shield the back-scattered electrons so that the back-scattered electrons reach the fluorescent body other than predetermined regions, thereby reducing the halation. In any case, as the rib 14 is higher, an effect of shielding the back-scattered electrons increases.
However, in the above-described conventional display panel, following problems may occur.
As described above, if the rib having the predetermined height is arranged on the black member on the side of the surface of the face plate opposite to the rear plate, the halation can be controlled. However, when aiming to achieve further high contrast and high color purity, it is necessary to further heighten the rib if it intends to sufficiently reduce the halation by the above method.
If the height of the rib increases, an amount of materials to be used to form the rib increases, and thus gas emitted from the rib increases. Consequently, since a degree of vacuum decreases, the fluorescent body, the electron source and the like deteriorate, whereby there is a fear that reliability decreases. Further, since the amount of the used materials increases, costs for manufacturing the apparatus increases resultingly. Furthermore, since it is difficult to form a more higher rib with a high degree of accuracy, it is difficult to obtain a desired shape of the rib.